Intensification of lignocellulosic bioethanol production process using continuous double-staged immersed membrane bioreactors.

Processing complexities associated with different lignocellulosic bioethanol production stages have hindered reaching full commercial capacity. Therefore, in this study efforts were made to remediate some issues associated with hydrolysis and fermentation, by the integration of immersed membrane bioreactors (iMBRs) into lignocellulosic bioethanol production process. In this regards, double-staged continuous saccharification-filtration and co-fermentation-filtration of wheat straw slurry was conducted using iMBRs at filtration fluxes up to 51.0 l.m-2.h-1 (LMH). The results showed a stable long-term (264 h) continuous hydrolysis-filtration and fermentation-filtration with effective separation of lignin-rich solids (up to 70% lignin) from hydrolyzed sugars, and separation of yeast cells from bioethanol stream at an exceptional filtration performance at 21.9 LMH. Moreover, the effect of factors such as filtration flux, medium quality and backwashing on fouling and cake-layer formation was studied. The results confirmed the process intensification potentials of iMBRs in tackling commonly faced technical obstacles in lignocellulosic bioethanol production.

Land use effects on phosphorus sequestration in soil aggregates in western Iran.

Cultivating native lands may alter soil phosphorus (P) distribution and availability. The present study aimed to determine the distribution of P in soil aggregates for different long-term land management practices. The partitioned P in labile (L), Fe/Al-bound, Ca-bound, organic pools, and total P in four aggregate size fractions were determined for five land uses (forest, vineyard after 30 years, wetland, alfalfa, and wheat cultivated soil after 20 years). Both native land uses (forest and wetland) were distinguished by high and low amounts of large macro- and micro-aggregates, respectively, compared with disturbed soils (vineyard, alfalfa, and wheat soils). Labile P in large macro-aggregates were higher in native land use when compared with the other land uses, which led to increasing lability of P and accelerated water pollution. Soils under native conditions sequestered more Ca-bound P in large macro-aggregates than the soils in disturbed conditions. Conversion of native lands to agricultural land caused enhanced organic P storage in aggregates smaller than the 2 mm from 31.0 to 54.3%. Soils under forest had 30% total P more than the vineyard for the aggregates >2 mm after 30 years land use change. However, the amount of P in smaller (<2 mm) sized aggregates was increased by 29% for the vineyard when compared with the forest. The P storage as bound Ca particles for the large macro-aggregates had negative correlation with the micro-aggregates.

Significance of physical weathering of two-texturally different soils for the saturated transport of Escherichia coli and bromide.

This study was carried out to investigate the transport of Escherichia coli NAR and bromide (Br) through repacked (R) and weathered (W) soil columns. A suspension containing E. coli NAR and Br were leached and the effluent from the weathered soil columns had greater contaminant concentrations than that from the repacked soil columns. The time to the concentration peak of (C(max)) E. coli NAR and Br increased in the order CL-W < SL-W < SL-R < CL-R. The breakthrough sequence suggests the formation of a heterogeneous soil pore network induced by weathering and the importance of accelerated flow in the weathered columns. The dual-permeability model in HYDRUS-1D software was used to simulate the E. coli NAR and Br transport parameters by inverse modeling. Parameters of the attachment-detachment model were calculated using the dual-permeability model parameters fitted to the BTCs of E. coli NAR. A greater attachment coefficient associated with soil repacking and the finer textured clayey soil demonstrated the importance of adsorbent site and smaller pore spacing in these treatments. Smaller attachment and adsorption isotherm coefficients in weathered soil columns suggest the need for further research to validate this as a predictive model for the risks for vadose zone contaminant transport.

Validation study of the s classification for melanoma patients with positive sentinel nodes: the Montreal experience.

BACKGROUND: Standard of care is to perform a complete lymph node dissection (CLND) in melanoma patients with positive sentinel lymph nodes (SLNs). However, less than 20% will have metastases in non-SLNs. The S classification was described to predict the non-SLN status, hoping to identify a subset of patients who can be spared the CLND. We tried to validate the feasibility and usefulness of this classification. MATERIALS AND METHODS: We performed a retrospective chart review. All melanoma cases between 1996 and 2006 were included, and 359 patients with SLN biopsies were identified. All pathology slides were reviewed with an emphasis on the S classification. RESULTS: There were 365 SLN biopsies performed. A total of 82 patients (22.8%) had positive SLNs, while 277 patients (77.2%) had negative SLNs. There were 22 patients classified as SI, 18 as SII, 37 as SIII, and 5 were unclassified. On CLND, only 10 patients (12.2%) had positive non-SLNs. None of these were classified as SI while 2 patients (11%) were classified as SII and 8 (22%) as SIII. The S category was found to be a predictor of non-SLN status, and this reached statistical significance (P = 0.044). On univariate analysis, only an increasing Breslow depth and ulceration were predictive of a non-SI status. CONCLUSION: Our results suggest that the S classification is easily feasible and predicts the status of non-SLNs. No patient with SI status was found to have additional non-SLN positive nodes. A larger-scale, prospective trial should be done to confirm these results and possibly spare patients the morbidity of CLND with a positive SLN.

Markov modelling of HIV infection evolution in the HAART era.

The aim was to investigate the impact of the main prognostic factors on HIV evolution. A multi-state Markov model was applied in a cohort of 2126 patients to estimate impact of these factors on patients' clinical and immunological evolutions. Clinical progression and immunological deterioration shared most of their prognostic factors: male gender, intravenous drug use, weight loss, low haemoglobin level (<110 g/l), CD8 cell count (<500/mm(3)) and HIV viral load (>5 log(10) copies/ml). Highly active retroviral therapy reduced the risks of clinical progression and immune deterioration whatever patients' CD4 cell count. Risk reductions were 41-60% for protease inhibitor-based and 27-68% for non-nucleoside reverse transcriptase inhibitor-based regimens. Three-year transition probabilities showed that only patients with a CD4 cell count >or=350 CD4/mm(3) could in most cases maintain their immunity. This model provides 'real life' transition probabilities from one immunological stage to another, allowing decision analyses that could help determine the beneficial therapeutic strategies for HIV-infected patients.

Influence of organic waste type and soil structure on the bacterial filtration rates in unsaturated intact soil columns.

Organic wastes are considered to be a source for the potentially pathogenic microorganisms found in surface and sub-surface water resources. Following their release from the organic waste matrix, bacteria often infiltrate into soil and may be transported to significant depths contaminating aquifers. We investigated the influence of soil texture and structure and most importantly the organic waste properties on the transport and filtration coefficients of Escherichia coli and total bacteria in undisturbed soil columns. Intact soil columns (diameter 16 cm and height 25 cm) were collected from two soils: sandy clay loam (SCL) and loamy sand (LS) in Hamadan, western Iran. The cores were amended with cow manure, poultry manure and sewage sludge at a rate of 10 Mg ha(-1) (dry basis). The amended soil cores were leached at a steady-state flux of 4.8 cm h(-1) (i.e. 0.12 of saturated hydraulic conductivity of the SCL) to a total volume of up to 4 times the pore volume of the columns. The influent (C(0)) and effluent (C) were sampled at similar time intervals during the experiments and bacterial concentrations were measured by the plate count method. Cumulative numbers of the leached bacteria, filtration coefficient (lambda(f)), and relative adsorption index (S(R)) were calculated. The preferential pathways and stable structure of the SCL facilitated the rapid transport and early appearance of the bacteria in the effluent. The LS filtered more bacteria when compared with the SCL. The effluent contamination of poultry manure-treated columns was greater than the cow manure- and sewage sludge-treated ones. The difference between cow manure and sewage sludge was negligible. The lambda(f) and S(R) values for E. coli and total bacteria were greater in the LS than in the SCL. This indicates a predominant role for the physical pore-obstruction filtration mechanisms as present in the poorly structured LS vs. the retention at adsorptive sites (chemical filtration) more likely in the better structured SCL. While the results confirmed the significant role of soil structure and preferential (macroporous) pathways, manure type was proven to have a major role in determining the maximum penetration risk of bacteria by governing filtration of bacteria. Thus while the numbers of bacteria in waste may be of significance for shallow aquifers, the type of waste may determine the risk for microbial contamination of deep aquifers.

Empirical study of the dependence of the results of multivariable flexible survival analyses on model selection strategy.

Flexible survival models, which avoid assumptions about hazards proportionality (PH) or linearity of continuous covariates effects, bring the issues of model selection to a new level of complexity. Each 'candidate covariate' requires inter-dependent decisions regarding (i) its inclusion in the model, and representation of its effects on the log hazard as (ii) either constant over time or time-dependent (TD) and, for continuous covariates, (iii) either loglinear or non-loglinear (NL). Moreover, 'optimal' decisions for one covariate depend on the decisions regarding others. Thus, some efficient model-building strategy is necessary.We carried out an empirical study of the impact of the model selection strategy on the estimates obtained in flexible multivariable survival analyses of prognostic factors for mortality in 273 gastric cancer patients. We used 10 different strategies to select alternative multivariable parametric as well as spline-based models, allowing flexible modeling of non-parametric (TD and/or NL) effects. We employed 5-fold cross-validation to compare the predictive ability of alternative models.All flexible models indicated significant non-linearity and changes over time in the effect of age at diagnosis. Conventional 'parametric' models suggested the lack of period effect, whereas more flexible strategies indicated a significant NL effect. Cross-validation confirmed that flexible models predicted better mortality. The resulting differences in the 'final model' selected by various strategies had also impact on the risk prediction for individual subjects.Overall, our analyses underline (a) the importance of accounting for significant non-parametric effects of covariates and (b) the need for developing accurate model selection strategies for flexible survival analyses.

Heat-shock protein 70 inhibits apoptosis by preventing recruitment of procaspase-9 to the Apaf-1 apoptosome.

The cellular-stress response can mediate cellular protection through expression of heat-shock protein (Hsp) 70, which can interfere with the process of apoptotic cell death. Stress-induced apoptosis proceeds through a defined biochemical process that involves cytochrome c, Apaf-1 and caspase proteases. Here we show, using a cell-free system, that Hsp70 prevents cytochrome c/dATP-mediated caspase activation, but allows the formation of Apaf-1 oligomers. Hsp70 binds to Apaf-1 but not to procaspase-9, and prevents recruitment of caspases to the apoptosome complex. Hsp70 therefore suppresses apoptosis by directly associating with Apaf-1 and blocking the assembly of a functional apoptosome.

Expression of Fas ligand in activated T cells is regulated by c-Myc.

The transcription factor c-Myc is important for the control of cell cycle progression, neoplasia, and apoptotic cell death. c-Myc dimerizes with its partner Max to form an active transcription factor complex. Little is known, however, about the transcriptional targets of c-Myc and their roles in c-Myc-induced cell death. Here we demonstrate that T cell activation-induced expression of Fas ligand (FasL, CD95-L, APO-1-L), which can induce apoptotic cell death in many different cell types, is regulated by c-Myc. Down-modulation of c-Myc protein via antisense oligonucleotides blocked activation-induced FasL mRNA and protein expression and functional FasL expression in activated T cells and T cell lines. Further, FasL promoter activity in T cells is driven by overexpression of c-Myc and inhibited by expression of dominant-negative mutants of c-Myc and Max. Our findings indicate that c-Myc controls apoptotic cell death in T cells through regulation of FasL expression.

Protein kinase ctheta cooperates with calcineurin to induce Fas ligand expression during activation-induced T cell death.

Activation-induced cell death is mediated by the TCR-induced expression of the Fas ligand (FasL) on the surface of T cells, followed by binding to its receptor Fas. FasL expression is induced by stimulating T cells with a combination of phorbol ester and Ca2+ ionophore, implicating a role for protein kinase C (PKC) in this process. However, the precise mechanisms that regulate FasL expression, including the contribution of distinct T cell-expressed PKC isoforms, are poorly understood. Herein, we report that PKCtheta, a Ca2+-independent PKC isoform that we have previously isolated as a PKC enzyme selectively expressed in T cells, plays an important role in these processes. A constitutively active PKCtheta mutant preferentially induced FasL expression and activated the corresponding gene promoter; conversely, a dominant-negative PKCtheta mutant blocked FasL expression induced by anti-CD3 or PMA plus ionomycin stimulation. Furthermore, PKCtheta synergized with calcineurin to provide a potent stimulus for FasL promoter activation. Full activation of the promoter required its binding sites for the transcription factors NF-AT, AP-1, and NF-kappaB. The biological significance of these findings is implicated by the finding that rottlerin, a selective PKCtheta inhibitor, blocked FasL induction by anti-CD3 or PMA plus ionomycin stimulation and, consequently, protected human Jurkat T cells and the mouse T cell hybridoma A1.1 from activation-induced cell death.

DNA damaging agents induce expression of Fas ligand and subsequent apoptosis in T lymphocytes via the activation of NF-kappa B and AP-1.

Apoptosis induced by DNA damage and other stresses can proceed via expression of Fas ligand (FasL) and ligation of its receptor, Fas (CD95). We report that activation of the two transcription factors NF-kappa B and AP-1 is crucially involved in FasL expression induced by etoposide, teniposide, and UV irradiation. A nondegradable mutant of I kappa B blocked both FasL expression and apoptosis induced by DNA damage but not Fas ligation. These stimuli also induced the stress-activated kinase pathway (SAPK/JNK), which was required for the maximal induction of apoptosis. A 1.2 kb FasL promoter responded to DNA damage, as well as coexpression with p65 Rel or Fos/Jun. Mutations in the relevant NF-kappa B and AP-1 binding sites eliminated these responses. Thus, activation of NF-kappa B and AP-1 contributes to stress-induced apoptosis via the expression of FasL.

HIV-1 Vpr suppresses immune activation and apoptosis through regulation of nuclear factor kappa B.

The HIV-1 accessory gene product Vpr can influence viral pathogenesis by affecting viral replication as well as host cell transcription and proliferation. We have investigated the effects of Vpr on host cell activation and confirm that it influences cellular proliferation. However, we have also found that Vpr modulates T-cell receptor (TCR)-triggered apoptosis in a manner similar to that of glucocorticoids. In the absence of TCR-mediated activation, Vpr induces apoptosis whereas in its presence, Vpr interrupts the expected induction of apoptosis. This regulation of apoptosis is linked to Vpr suppression of NF-kappa B activity via the induction of I kappa B, an inhibitor of NF-kappa B. Further, Vpr suppresses expression of IL-2, IL-10, IL-12, TNF alpha and IL-4, all of which are NF-kappa B-dependent. The effects of Vpr could be reversed by RU486. Our finding that Vpr can regulate NF-kappa B supports the hypothesis that some aspects of viral pathogenesis are the consequence of cell dysregulation by Vpr.

Regulation of the Fas apoptotic cell death pathway by Abl.

Relatively little is known about oncogene involvement in the regulation of Fas-mediated apoptosis. Inhibition of Fas-induced cell death by the bcl-2 oncogene has been demonstrated to be only partial. In light of a growing body of evidence for the Abl kinase as a negative regulator of cell death, we sought to determine whether Abl expression could protect against Fas-mediated cell death. To address this question, we utilized two separate strategies. In the first, we expressed human Fas in K562, a chronic myelogenous leukemia cell line, which constitutively expresses bcr-abl and examined the effects of Fas ligation in these cells. Fas-positive K562 transformants (K562.Fas) were found to be protected against Fas-mediated cell death. However, down-regulation of Bcr-Abl protein levels in K562.Fas cells using antisense oligonucleotides targeted to bcr-abl mRNA rendered these cells highly susceptible to Fas-induced death. In the second approach we utilized a Fas-positive HL-60 cell line, which we transfected with a temperature-sensitive mutant of v-Abl. HL-60.v-Ablts transfectants were found to be protected from Fas-induced apoptosis at the permissive but not the restrictive temperature for the Abl kinase. Taken together, these observations identify the Abl kinase as a negative regulator of Fas-mediated cell death. Since Abl was also found to block apoptosis mediated by ceramide, a recently proposed downstream effector of the apoptotic pathway initiated by Fas, we propose that Abl exerts its protective effects downstream of the early Fas-initiated signaling events.

FAS-induced apoptosis is mediated via a ceramide-initiated RAS signaling pathway.

Fas receptor-induced apoptosis plays critical roles in immune homeostasis. However, most of the signal transduction events distal to Fas ligation have not been elucidated. Here, we show that Ras is activated following ligation of Fas on lymphoid lines. The activation of Ras is a critical component of this apoptotic pathway, since inhibition of Ras by neutralizing antibody or a dominant-negative Ras mutant interfered with Fas-induced apoptosis. Furthermore, ligation of Fas also resulted in stimulation of the sphingomyelin signalling pathway to produce ceramides, which, in turn, are capable of inducing both Ras activation and apoptosis. This suggests that ceramides acts as second messengers in Fas signaling via Ras. Thus, ligation of the Fas molecule on lymphocyte lines induces activation of Ras via the action of ceramide, and this activation is necessary, but not sufficient, for subsequent apoptosis.

Proteolysis of fodrin (non-erythroid spectrin) during apoptosis.

Several recent studies have implicated proteases as important triggers of apoptosis. Thus far, substrates that are cleaved during apoptosis have been elusive. In this report we demonstrate that cleavage of alpha-fodrin (non-erythroid spectrin) accompanies apoptosis, induced by activation via the CD3/T cell receptor complex in a murine T cell hybridoma, ligation of the Fas (CD95) molecule on a human T cell lymphoma line and other Fas-expressing cells, or treatment of cells with staurosporine, dexamethasone, or synthetic ceramide. Furthermore, inhibition of activation-induced apoptosis by pretreatment of T hybridoma cells with antisense oligonucleotides directed against c-myc also inhibited fodrin proteolysis, confirming that this cleavage process is tightly coupled to apoptosis. Fodrin cleavage during apoptosis may have implications for the membrane blebbing seen during this process.

Cell-autonomous Fas (CD95)/Fas-ligand interaction mediates activation-induced apoptosis in T-cell hybridomas.

A number of murine T-cell hybridomas undergo apoptosis within a few hours of activation by specific antigens, mitogens, antibodies against the T-cell antigen receptor, or a combination of phorbol ester and calcium ionophore. This phenomenon has been extensively studied as a model for clonal deletion in the immune system, in which potentially autoreactive T cells eliminate themselves by apoptosis after activation, either in the thymus or in the periphery. Here we show that the Fas/CD95 receptor, which can transduce a potent apoptotic signal when ligand, is rapidly expressed following activation of T-cell hybridomas, as is its functional, membrane-bound ligand. Interference with the ensuing Fas/Fas-ligand interaction inhibits activation-induced apoptosis. Because T-cell receptor ligation can induce apoptosis in a single T hybridoma cell, we suggest that the Fas/Fas-ligand interaction can induce cell death in a cell-autonomous manner.

Promotion and inhibition of activation-induced apoptosis in T-cell hybridomas by oncogenes and related signals.

The Two Signal: Death/Survival Model suggests that cellular proliferation and physiological cell death should be intimately associated such that, in the absence of external influences, a normal cell departing from rest will have an equal probability of undergoing either process. The c-Myc protooncogene product has been implicated in cell cycle progression and in the control of gene expression, and more recently c-Myc has also been seen to promote apoptotic cell death. As predicted from the model, c-Myc-induced apoptosis is inhibited by growth factors or other anti-apoptotic signals including those provided by some oncogenes. Here, we discuss experiments that test the Two Signal: Death/Survival Model in the phenomenon of activation-induced apoptosis in T-cell hybridomas. Ligation of the antigen receptor on these cells leads to activation, resulting in cytokine production and apoptosis. Inhibition of c-Myc expression by addition of antisense oligodeoxynucleotides or transforming growth factor beta inhibits this form of apoptosis. Because c-Myc is known to bind to several cellular proteins, including Max, we further examined the effects of expression of a dominant negative Max on activation-induced apoptosis. We found that this Max mutant, which interferes with the function of the Myc/Max heterodimer, inhibits the induction of apoptosis by antigen receptor ligation. Thus, both Myc and Max play roles in activation-induced apoptosis, presumably via control of gene expression. Further, as predicted, signals generated from growth factor receptors or the v-Abl oncogene interfere with activation-induced apoptosis. In contrast, the anti-apoptotic effects of Bcl-2 are not active in this form of apoptosis. Finally, a role for Fas/Fas-ligand interactions in activation-induced apoptosis is considered.

Functional Myc-Max heterodimer is required for activation-induced apoptosis in T cell hybridomas.

T cell hybridomas respond to activation signals by undergoing apoptotic cell death, and this is likely to represent comparable events related to tolerance induction in immature and mature T cells in vivo. Previous studies using antisense oligonucleotides implicated the c-Myc protein in the phenomenon of activation-induced apoptosis. This role for c-Myc in apoptosis is now confirmed in studies using a dominant negative form of its heterodimeric binding partner, Max, which we show here inhibits activation-induced apoptosis. Further, coexpression of a reciprocally mutant Myc protein capable of forming functional heterodimers with the mutant Max can compensate for the dominant negative activity and restore activation-induced apoptosis. These results imply that Myc promotes activation-induced apoptosis by obligatory heterodimerization with Max, and therefore, by regulating gene transcription.

Probing the opioid receptor complex with (+)-trans-SUPERFIT. II. Evidence that mu ligands are noncompetitive inhibitors of the delta cx opioid peptide binding site.

Previous studies delineated two classes of delta binding sites; a delta binding site not associated with the opioid receptor complex, termed the delta ncx site, and a delta site associated with the opioid receptor complex, termed the delta cx site. The delta ncx site has high affinity for [D-Pen2,D-Pen5]enkephalin, and is synonymous with what is now identified as the delta 1 binding site. Pretreatment of membranes with the delta-selective acylating agents FIT, or (+)-trans-SUPERFIT, deplete membranes of the delta ncx binding site, which permits the selective labeling of the delta cx binding site with [3H][D-Ala2,Leu5]enkephalin. The present study compared the properties of the delta cx binding site present in brain membranes pretreated with (+)-trans-SUPERFIT with the properties of the delta cx site present in untreated membranes. The major findings are: 1) pretreatment of membranes with (+)-trans-SUPERFIT decreased the IC50 values of delta-preferring drugs, and increased the IC50 values of mu-preferring drugs, for the delta cx binding site; 2) the degree of delta selectivity was highly correlated with the magnitude of the (+)-trans-SUPERFIT-induced shift in the IC50 values; 3) the ligand-selectivity patterns of the mu and delta cx sites present in (+)-trans-SUPERFIT-pretreated membranes were poorly correlated; 4) whereas mu-preferring drugs were noncompetitive inhibitors of [3H][D-Ala2,Leu5]enkephalin binding to the delta cx site, delta-preferring drugs were competitive inhibitors.(ABSTRACT TRUNCATED AT 250 WORDS)